I have the H&R spacers on my Street Serpent. It is a concentric spacer and I was very impressed by the quality. I went that direction instead of the other offerings as they do not require you to remove the wheel hubs to replace the stock studs with the longer competition coupe studs. The only downside is that you do need to cut the stock wheel studs as they protrude past the 25mm spacer. This might not be required on all wheels - but it was required with the stock 5 spokes.
I've got a number of pics in my gallery or I can post some new ones if you like as I love to show off my Street Serpent and actually need new pics with my 5 spokes post CalChrome - BLING, BLING!
Treesnake - why you always gotta temp me with the TT talk? Pretty much decided that I'm going to wait till next winter before doing anything else and just drive and drive this year. That is unless I go to a quaiffe/gears, new motor and trans mounts, and some headers

. Only thinking about the headers as I am still having some issues getting my current exhaust to fit properly with the opening on the Serpent kit and I certainly don't want a repeat of the paint issues I had with the sills.